The present invention relates generally to the field of positioning and, in particular, to systems and methods suitable for indoor location positioning.
Indoor position location is becoming increasingly important in today's mobile wireless devices environment. Whereas it took some time for outdoor location services to become widespread after the technology was available, today the applications for indoor position location is racing ahead of available technical solutions. Many technologies have been used for outdoor position location, chief among them are the Global Positioning System (GPS) using orbiting satellites that transmit timing and ranging signals that enable a receiver to calculate its position accurately. In addition to GPS a number of other technologies have been proposed with various degrees of adoption including cellular base-station triangulation and trilateration.
Unfortunately, technologies employed for outdoor position location perform poorly for indoor position location. This is because the signal of these systems is either missing or very weak indoors, as in the case with GPS, or the signal arrives with significant multipath to render it inaccurate for indoor positioning.
Some proposed systems attempt use available indoor Wi-Fi wireless signals to aid in determining the indoor position of a wireless portable device. Unfortunately, Wi-Fi radio-frequency (RF) environments can change unpredictably over time and even under ideal conditions the location may only be accurate to a resolution of a few meters. Other proposed systems employ wireless beacons that use the Bluetooth wireless protocol to narrow down the location of a wireless device. Such systems rely on detecting proximity to one of such beacons and therefore requires deploying a different beacon near every point of interest in the indoors environment. Only a few feet away from a beacon, the estimate of the position is no more accurate than one using Wi-Fi signals. These systems rely on detecting a certain router or a beacon with a certain preregistered code associated with a known and published physical location to establish approximate location and then use a Received Signal Strength Indicator (RSSI) to further narrow down the location. Such methods are limited in the ultimate resolution they can achieve in a large indoors area. Also while the first relies on already available low accuracy and often varying Wi-Fi signals, the beacon method requires blanketing an indoor area, such as a department store for example, with a large number of active beacons that need constant power source and physical management as the store changes promotions and refashions internal displays. In addition, those methods are either too inaccurate or too cumbersome to adopt in a domestic residential environment. Furthermore, since such methods rely on RSSI measurements, signal penetration through walls and floors results in a major drawback for both commercial as well as enhanced E911 services since with wall and floor penetration the location of an individual cannot be narrowed down to an exact room or an exact floor.
Other proposed systems for indoor position location are based on Ultra-Wide Band (UWB) methods, for example, as described in “Ultra-Wideband Positioning Systems” by Sahinoglu, Gezici and Guvenc, 2008. Unfortunately, such systems depend on a powered active radio-frequency identification (RFID) tag for proper operation and may include bulky batteries. With continuous tracking of numerous users within some vicinity, battery life becomes impractically short. In addition, the RFID tags may be costly.
Other proposed systems use coded LED lighting to determine indoor position location. Such methods rely on the camera of a mobile device detecting a coded lighting flicker from an LED light fixture to determine location. Unfortunately, there is a significant time where the mobile device of an individual is placed in a carrying bag or in a pocket. Also, in most cases, a costly replacement of numerous lighting fixtures is needed to accommodate the new LED bulbs. Furthermore, the accuracy of such technologies is only able to provide approximate location, such as location within a room, rather than determine actual location with sufficient resolution for commercial and residential applications demand accuracy on the order of few centimeters. Similar limitations occur when using infrared beacons.
Other proposed systems use ultrasonic sound waves. Such systems require retrofitting indoor spaces with multiple wireless/ultrasonic beacons and/or receivers needing their own power sources. In addition, ultra-sonic transmitting and receiving transducers may be too bulky and consume too much power for a mobile device or a battery operated beacon. In addition, ultrasound is severely muffled in a person's carrying bag or inside a pocket.